A motor drive control apparatus driving and controlling a plurality of electric motors has been used as one type of the motor drive control apparatus applied to a hybrid vehicle. International Publication No. WO2003/015254 for example discloses in FIG. 9 a configuration of a motor drive control apparatus used for a hybrid vehicle of a two-motor system including electric motors M1 and M2.
FIG. 9 of International Publication No. WO2003/015254 conceptually shows a common control apparatus as the control apparatus for driving and controlling electric motors M1 and M2. As for the actual motor drive control apparatus, however, if a single control apparatus (electronic control unit: ECU for example) is used to perform control operation for both of motors M1 and M2, an excessively heavy processing load is placed on the ECU, and accordingly a high-performance ECU may be required.
Therefore, a practical configuration is the one including control apparatuses (ECU) provided separately and independently for respective electric motors so that each control apparatus (ECU) performs control operation for driving the associated electric motor. This configuration enables a motor drive control apparatus to be implemented without excessive processing load on each control apparatus and without excessive demand for the processing speed of the control apparatus, namely without increasing the cost for each control apparatus (ECU).
In the case, however, where control apparatuses (ECU) are provided separately and independently for respective electric motors, a problem arises when motor M1 and motor M2 are cooperatively controlled. One example of this cooperative control is electric power balance control performed for restricting, within a certain range, the total input/output electric power to/from a plurality of electric motors as a whole.
In order to speedily perform the electric power balance control, it is preferable in terms of readiness to implement a control configuration managing the electric power balance by one of a plurality of separately provided control apparatuses and restricting as required the electric power of the electric motor associated with that control apparatus. The control configuration, however, could lose synchronization between a plurality of electric motors in terms of the data and information used for the electric power balance control, due to an influence of the time for communication between the control apparatus performing the electric power balance control and other control apparatuses. In other words, recognition of data and information is delayed by the time consumed for communication. As a result, particularly in a period in which the electric motor output (rotational speed, torque) varies, the possibility that appropriate electric power balance control is impossible cannot be denied.